I am trying to accomplish a task to allow users modify and
view the data from DataGrid service, but the problem I have right
now is that it is based on the selections the users have made using
check boxes, which this portion is written in Actionscript.

I stored the selection into a string, and try to use
HTTPService to "POST" the data, and it did not return me anything
from my DataGrid. Could someone please help me with the syntax of
how to allow my two defined string variables be posted to the
service correctly?